The purpose of this project is to characterize the longitudinal course of pulmonary function in patients with cystic fibrosis, including profiling ofthe infection history of individuals. In the course of these analyses, methods for summarizing the clinical course for individual patients are being developed, as well as determination of the relationship of clinical and infection history to factors such as gender, the nature of the cystic fibrosis mutation (genotype), and age. Predictive models of change in pulmonary function based upon such factors, as well as prior course, will also be considered.